1. Field of the Invention
The invention in general relates to acoustic imaging systems, and particularly to a system utilizing an acoustic lens.
2. Description of the Prior Art
Acoustic lenses are utilized in underwater imaging systems in view of their capabilities of producing multiple acoustic beams. In general, an object to be viewed is insonified by means of an acoustic transmitter and reflections from points on the target are focused by means of the acoustic lens onto a transducer array. The output signals provided by the transducer array are processed to yield a display representative of the insonified target.
The action of the acoustic lens is such as to focus onto a focal surface occupied by the transducer array. Although the transducer array is generally planar, the lens actually focuses onto a curved focal surface so that with a relatively large field view, for example 15.degree., the image is out of focus with increasing distance from the lens axis thus causing a severe degradation of the final display.